Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$76.71	7.421%	$82.4026	$82.40	$82.40	$82.40
Purchase #2	$147.89	11.778%	$165.3085	$165.31	$165.30	$165.30
Purchase #3	$202.96	6.666%	$216.4893	$216.49	$216.50	$216.50
Purchase #4	$211.27	6.351%	$224.6878	$224.69	$224.70	$224.70
Purchase #5	$193.37	3.650%	$200.428	$200.43	$200.45	$200.40
Purchase #6	$6.58	6.438%	$7.0036	$7.00	$7.00	$7.00
Purchase #7	$131.61	13.718%	$149.6643	$149.66	$149.65	$149.70
7 purchase totals =	$970.39		$1,045.9841	$1,045.98	$1,046.00	$1,046.00